1. Field of the Invention
This invention relates to a signal transmission control apparatus applied to telephone service, and in particular to no-ringing service, by which signal transmission is effected without ringing the usual telephone apparatus.
2. Description of the Prior Art
In no-ringing service, an exclusive device acting as a signal transmission control apparatus is connected (set) to a telephone line in parallel with respect to a usual telephone apparatus in each house. A signal transmission line is formed between the telephone line and a terminal device, by the fact that only the exclusive device is called separately through the telephone line by adding a calling signal, to which the usual telephone apparatus does not react and which makes only the exclusive device work.
This no ringing service is now available also in Japan. However, the protocol therefor (communication procedure or communication regulation) is different for every country and it has not yet been standardized.